JPS641032B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device that fixes a toner image on a support material by a rotating body involved in fixing, and more specifically, the present invention relates to a fixing device that fixes a toner image on a support material by a rotating body involved in fixing. The present invention relates to a fixing device.

Conventionally, in a fixing device that uses, for example, a pair of fixing rollers as the rotating body, an anti-offset liquid such as silicone oil is applied to the surface of the roller for fixing the toner image to a supporting material for supporting the toner image in order to improve release properties. things are being done.
However, there is no method for changing the coating amount depending on the material of the support material. The present invention was researched and invented for the purpose of solving problems caused by the material of the support material.

The heat fixing of a multicolor toner image in a color copying machine will be described below. In the case of this color copying machine, for example, there is a method of completely melting and mixing three color toners such as cyan, magenta, yellow, etc., but since the toner is heated enough to completely melt and mix, the toner has a strong adhesive property. have. Further, the amount of toner applied to the support material is also large. Therefore, the toner is more likely to adhere to the surface of the fixing roller than when forming a monochromatic image, and the amount of toner attached is also large, which tends to cause offset to the fixing roller and wrapping of the support material. Therefore, it is essential to apply the anti-offset liquid to the surface of the fixing roller, and the amount of the anti-offset liquid applied must be large. For example, to fix an A4 size full color image transferred to plain paper, the amount of silicone oil applied is 50 mg/sheet, which is several times the amount applied when fixing a black and white image of the same size.

When such a large amount of anti-offset liquid is applied, if the support material is plain paper, most of the applied anti-offset liquid will be diffused and absorbed into the paper fibers in non-image areas or areas with little toner adhesion. Ru.
Therefore, there is almost no discomfort or strange feeling when holding the supporting material after fixation.

However, if the support material is made of a material that does not absorb the anti-offset liquid, such as a transparent film sheet for OHP, a thick film of anti-offset liquid will form on the surface of the support material after fixing, causing problems in appearance and texture for the user. This also affects the image condition, such as unevenness in the projected image due to uneven application of the offset prevention liquid.

Furthermore, even if the support material itself is absorbent of the anti-offset liquid, the fixed image is affected by differences in the amount of coating and the absorbency.

In view of the above-mentioned problems, the present invention provides a new fixing device that can maintain good fixing performance regardless of the material of the support material by controlling the amount of anti-offset liquid applied according to the absorbency of the anti-offset liquid of the support material. This is what we provide.

A detailed explanation of the present invention will be given below with reference to the drawings.

FIG. 1 shows one embodiment of the present invention, which is an example applied to a heat fixing device. Reference numeral 1 denotes a fixing roller that rotates clockwise and has a silicone rubber layer 3 coated on the surface of a metal pipe 2 to prevent offset, and the image supporting surface of the support material is pressed against the fixing roller 1. A pressure roller 4 and a heating roller 8 are provided in pressure contact with the fixing roller 1 and sandwiching the fixing roller 1 between them. The rollers 4 and 8 rotate counterclockwise and have the same structure, with Teflon layers 6 and 10 coated on the surfaces of metal pipes 5 and 9, and infrared lamps 7 and 11 disposed inside them. It is something that exists. The support material supporting the toner image is conveyed while being held in the nip between the fixing roller 1 and the pressure roller 4, where the toner image is heated and melted and fixed to the support material.

Reference numeral 12 denotes a cleaner that comes into contact with the circumferential surface of the roller 8, and the roller 8 removes offset toner on the surface of the fixing roller 1, and the roller 8 removes the offset toner for cleaning. 15 is a coating felt that pumps up and applies the silicone oil in the container 13 to the circumferential surface of the roller 8, and is pressed against the roller 8 for a predetermined time;
Or, by contact, this silicone oil is applied to the roller 8 and then to the circumferential surface of the fixing roller 1. This coated felt 15 is attached to the rotating shaft 1 together with the presser plate 16.
7 and rotary solenoid 18
The roller 8 is moved by a tension spring 19 between a coating position in which it contacts the roller 8 and a non-coating position in which it does not contact it.

Further, a scraper 20 that can be moved toward and away from the surface of the fixing roller 1 to remove excess silicone oil is disposed on the surface of the fixing roller 1. This scraper 20 has a rotating shaft 2
1, and the rotary solenoid 22
and the tension spring 23, it can be brought into contact with and separated from it in the same way as the felt 15. A device for controlling the operation of the rotary solenoids 18 and 22 will be described later.

Now, when a support material 24 having a toner image 25 (for example, composed of toner of three colors such as cyan, magenta, and yellow) corresponding to a document is sent between the pair of fixing rollers 1 and 4 by a known image forming method. The control means 27 for controlling the operation time of the rotary solenoids 18 and 22 is activated in response to the signal detected by the detection means 26 for detecting the silicone oil absorbency of the support material 24, and the rotary solenoid 18 or 18 and 22 are activated. Therefore, the felt 15 supplies silicone oil to the heating roller 8 in an amount suitable for the supporting material, and then the oil is distributed almost uniformly onto the surface of the fixing roller 1 at the nip between the rollers 8 and 1. It is controlled so that it is applied evenly.

As a result, the surface of the support material 24 that contacts the roller 1 is coated with silicone oil in an amount necessary and sufficient to prevent offset of the support material 24.
This enables good fixing, saves on silicone oil, and solves the above-mentioned problems caused by the material of the support material, resulting in excellent images.

When the support material 24 having the toner image 25 is sent between the pair of fixing rollers 1 and 4 to be fixed, the rotary solenoid 18 operates for a certain period of time, and an amount of silicone oil suitable for preventing offset of the support material is applied to the heating roller. It is applied to 8 surfaces. solenoid 1
The operating time of 8 is about 2 seconds for A4 size plain paper.
In the case of A4 size OHP sheets (for example, polyester film base), it is about 1 second,
When fixing OHP sheets, compared to fixing plain paper,
The amount of silicone oil applied is halved.

This switching of the silicone oil application time between plain paper and OHP sheets is performed after paper feeding is detected by a micro switch and by detecting the difference in transmitted light of the toner support material using a combination of a lamp and a light receiving element before transfer.

In this way, when fixing an OHP sheet, the rotary solenoid 22 is operated for a certain period of time based on clock control or a signal from a microswitch 28 that determines the passage timing of the toner support material, and removes excess silicone oil from the surface of the heating roller 1. It also makes it uniform and enables good fixing.

Next, a block diagram of the control of the above embodiment is shown in FIG. 2, and a flowchart thereof is shown in FIG.

This will be explained below using these two figures. 28 is
This is a micro switch that detects whether or not paper has been fed. A photo sensor 31 detects a difference in transmitted light of the toner support. In the case of OHP, it is detected brightly, and in the case of paper, it is detected darkly, so in combination with the micro switch 28, it can be determined whether the fed paper is OHP or paper. This part may be a circuit that provides a signal indicating that it is OHP by manual operation input.

These signals enter a control circuit 29 and are processed to operate the oil application rotary solenoid 18 and the scraper rotary solenoid 22. The temporal processing of control circuit 29 is carried out in accordance with clock circuit 30. Inside the control circuit 29, processing as shown in FIG. 3 is performed.

First, the presence or absence of paper is detected by the input from the micro switch ₂₈₁ , and when the clock timing reaches the timing for oil application and scraper operation, it is determined whether it is OHP or not. operates for the duration of the clock. In the case of an OHP, the oil application rotary solenoid 18 and the scraper rotary solenoid 22 operate during a predetermined clock period. In the case of OHP, the clock is set so that the operating time of the oil application solenoid 18 is shorter than in the case of plain paper. When fixing OHP sheets, the amount of silicone oil supplied to the heating roller is smaller than when fixing plain paper, but this does not affect the durability of the heating roller's silicone rubber or toner offset for the following reasons. There is no.

One is that when fixing OHP sheets, it has never been said that a considerable proportion of the amount of silicone oil supplied is absorbed by the toner support, as is the case when fixing plain paper. The high proportion of silicone oil is effective in preventing this.

In addition, the number of OHP sheets processed at a time is only a few dozen sheets or less, which is far less than that of plain paper. The silicone oil contained in the tube gradually seeps out, contributing to the prevention of offset, and from this point of view as well, it is possible to supply a small amount of oil.

Furthermore, another effect of this embodiment is that if a large amount of silicone oil is applied to the pair of fixing rollers, when an OHP sheet passes through the pair of fixing rollers, one of the pair of fixing rollers, for example in FIG. Although there is a tendency to wrap around the surface of the pressure roller 4 due to the distortion of the heating roller 1 that is formed, it also has the effect of preventing this. This tendency to wrap occurs because pressure is applied to the sheet with a large amount of oil interposed between the OHP sheet and the surface of the pressure roller 4, so there is no air space between the sheet and the roller, and the sheet is softened by heating. This occurs because a curling force is exerted on the pressure roller side in this state, and is the cause of jamming.

In FIG. 1, a scraper 20 is provided to limit the amount of silicone oil on the surface of the fixing roller 1, but this is not essential, and it is possible to more reliably apply the amount of silicone oil to the nip between the fixing roller 1 and the pressure roller 4. In terms of communication, it is possible to obtain better effects. Further, by providing the scraper 20, the operation for removing excess silicone oil becomes more reliable, and the amount of oil applied to the surface of the pressure roller 4 can be further reduced. In this sense, the scraper 20 may be provided in contact with the pressure roller 4.

Although silicone oil was used in the above embodiment, other anti-offset liquids can be used without being limited thereto. Further, the method of applying the offset prevention liquid and the method of controlling the same are not limited to those described above, and various control methods and application methods can be applied to the present invention. For example, instead of a rotary solenoid, a cam may be operated to control the coating amount, or the pressure with which the fixing rotor presses the coating felt may be controlled to be adjusted depending on the material of the support material. Further, instead of using a sensor to determine the material of the support material, the operator may manually select the offset prevention liquid application amount selection switch provided in the apparatus according to the material of the support material.

Furthermore, even better effects can be obtained if the present invention employs a method of controlling the coating amount as an additional element in consideration of changes in the anti-offset liquid absorbability of the support material due to changes in humidity. Of course, the present invention can be applied to monochrome or multi-color toner images, and can also be applied to pressure fixing.

As described above, the present invention makes it possible to supply an appropriate amount of anti-offset liquid to the support material, to enable fixing such that the image on the support material becomes an excellent clear image, and to efficiently consume and waste the anti-offset liquid. It is the one that has been eliminated.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a roller fixing device according to an embodiment of the present invention, FIG. 2 is a block diagram of another embodiment of the present invention, and FIG. 3 is a flowchart of FIG. 2. 1... Fixing roller, 4... Pressure roller, 8...
Heating roller, 13... Silicone oil, 14...
...Applying felt, 19...Scraper, 17,
21...Rotary solenoid.

Claims (1)

[Scope of Claims] 1. In a fixing device that applies an anti-offset liquid to a rotating body involved in fixing, the amount of the anti-offset liquid applied is controlled according to the absorbency of the anti-offset liquid of the material of the support material that supports the toner image. A fixing device comprising a control means.